Gyroscopic navigational instru



1940- I D. G. K. Moss 2,220,457

. GYROSCOPIC NAVIGATIONAL INSTRUMENT Filed June 15, 1957 8 Sheets-Sheet 1 D, eurse Km M055.

\NvEN Q Nov. 1940- D. G. K. Moss GYROSCOPIC NAVIGATIONAL INSTRUMENT 8 SheetsSheet 2 Filed June- 15, 1957 Dau3\0$ Geor e S fin.

Nov. 5, 1940; oss 2,220,457

eYnosc'orlc NAVIGATIONAL INSTRUMENT Filed June 15, 1957 a Sheets-:Sheet 5 dd 46 66 J6 6'9 4/ 6'3 W J2 V v beu hs Geese. 3 1 55 IN EHTOg NOV. 5, 1940. I D 055 2,220,457

GYRoscoPic NAVIGATIONAL INSTRUMENT -Filed June 15, 1937 a Sheets-Sheet 4 9 65 ZZZ;

DQQSGS Geese Kmfl MOSS \NVENTOR L wywl Nov. 5, 1940. I G oss 2,220,457

GYROSCOPIC NAVIGATIONAL INSTRUMENT Filed June 15, 1937 s Sheets-Sheet 5 Douglagemg. K fiwj Moss lHVENiTog, a; Q fiW M HL a. A'rn I Nov. 5, 1940. D; G. K. MOSS, 2,220,457

GYROSCOPIC. NAVIGATIONAL INSTRUMENT Filed June 15, 195? 8 Sheets-Sheet 6 NOV. 5, 1940. G. M055 1 2,220,457

GYROSCOPIC NAVIGATIbNAL INSTRUMENT Filed June 15, 1957 8 Sheets-Sheet 8 \NVENT E: mw

. B ATTL sary to provide for setting'the gyroscopescale to -Patented Nov. 5, 1940 UNITED [STATES PATENT; OFFICE f Douglas George King Moss, Sanderstead, England,

assignor to Mechanism Limited, Croydo'n, England, a limited corporation of Great Britain Application June 15, 1937, Serial Nit 148,327 e In Great Britain June 19, 1936 scams. (01. 33-204)" This invention relates to improvements in yroscopic navigational instruments and more particularly to azimuth indicating free gyroscopic 111- struments of the typesometimes referred to as directional gyroscopes having three degrees of freedom. As is known with such instruments, it is necesa desired course reading and for restoring the scale to the desired course should it have wandered'due to frictional or other causes. to, this result has been achieved by more orless complicated mechanical means forilocking the gyroscope with respect to one of its axes and rotating it and/ or the scale with respect to its other axis, 1. e., in azimuth. The known instruments not only suffer disadvantage due to the' complication of the mechanical means but suffer a further important disadvantage in that the scale is brought to the desired position by continual Now, a pilot may not be able conveniently to spare -his-hand for continued manual operation,

and, with a view to obviating this necessity whilst 1 at the same time overcoming the other disadvantages of the known constructions, the chief object of the present invention is to provide an in-,

strument in which the scale is set or re-set by precession of the gyroscope.

A further object is to provide an instrument such that the craft in which it is installed can normally perform a complete roll without disturbance of the instrument reading.

According to the present invention, the scale ring is fast with'the outer gimbal and'the ref vention, means are provided for erecting the gyro-wheel with respect to the outer gimbal.

The couple may be created by jets of air, me

chanical means or electro-magnetic means as is hereinafter made apparent.

In order that the inventionmay be clearly understood and readily carried into effect, certain embodiments thereof are hereinafter more fully described with reference to the accompanying Hitherembodiments of the invention, like parts bear like drawings which are given by way'of'example only and not of limitation.

In these drawings-g- Figure 1 is a front view of the instrument.

Figure 2 is a front viewofnone form of mecha- 5 nism without the face plate.

Figure-3 is a side sectional elevation of the mechanism of Figure 2.

' Figure 4 is a plan view thereof. Figure 5 is a sectionon the line 5-5 of Figure 4 shown on a. larger scale. Figure 6 is a section on the line also on a larger scale.

Figure 7 is a section on the line 1-1 of-Figure 6. Figure 8 is a front view of another form of mechanism with the face plate.

-Figure-9 is a plan view of same. 1

Figure 10*is a side elevation seen from the right. Figure 11 is a. side elevation seen from the left. Figure 12-is a perspective view thereof.

' Figure 13 is an under plan view.

6-6 of Figure 3 Figures 14 and 15 are detail views of thecam on Figure 19 is aside elevation thereof.

' Figure 20 isa detail plan view of a modified form of innergimbalerecting control valve.-

In the description which follows of the various reference numerals."

' Referring now to thesaid drawings and in particular to Figures 1 to 7 thereof, an air driven gyro wheel I, spinning about a normally horizontal axis and'mounted in-an air-tight housingZ which constitutes the inner gimbal, is pivoted about a fore-and-aft axis to an outer gimbal 3 which is, in turn, pivoted about a vertical axis to "the main frame 4 which forms part of the outer air-tight instrument case 5.

I Air is led in, at the back of the instrument, through filter gauges 6, to a chamber 1 front which extends an inlet duct 8 which passes through thesolid frame l-and opens into an annular channel Q'in the'plug 10. A duct H leads from the channel 9 to the hollow core 12 of the plug III, the. end of which is truncated and recessed to receive the .ball 13. A'similar truncated hard-steel bearing-element 14, forming the other half of the bearing, is carried by the outer gimbal 3 which is also provided with a tubular extension or shroud I5 which takes into a suitable aperture in the frame 4 and surrounds the plug "1. One

or more ducts I6 in the-truncated portion of the plug I6 lead from its core I2 to the bore of the extension I5 and'corresponding ducts I1 are provided in the element I4 for permitting the air to enter the duct' I6 in the outer gimbal 3, which pivots which is hollow for the purpose of leading air through to drive the gyro wheel I. This pivot comprises a hollow spindle I3, retained by locking screws 26 and apertured at 2I and 23 to allow the the part .33 which has a tubular extension 34 which surrounds the trunnion 26'. oppositely disposed air exit orifices are provided in the extension 34, which orifices are concentric to a horizontal axis. The orifices are'normally partially obstructed by a semi-circular extension of the trunnion 29. Thus, when the innergimbal 2 departs from normal position, one of the orifices is opened to a greater extent whilst the other is closed a similar amount, setting up an unbalance of the emergent air which tends to blow the outer gimbal about its vertical axis but in eilfect, due to precession of the gyro-wheel, restores the inner gimbal to normalwith respect to the outer gimbal v position by a locking nut 63'.

and a resumption of balance of theair jets; Theupper outer gimbal pivot comprises a hard-steel truncated element 61, bearing a ball 68 and cooperating element 63, extending through and threadedlyengaging the frame 4, being locked in The accuracy of the balance of the inner gimbal 2 is assured by'weights I0 threadedly engaging screwed rods II, co-axial with theaxis of the gyro-wheel, which tp'eights are locked in adjusted position by lock nuts I2. The outer gimbal 3 is similarly balanced by weights I3 and lock nuts 14 on the threaded rods I5.

A scale ring 36 is carried by the outer gimbal 3, which ring bears degree marks 31' and numerals 36 visible through the aperture 46 in the face plate 4I Figure 1). A representation of an aeroplane 42 having an extended nose serves as indicator and adjacent the tail of the pictured aeroplane 42 is a bubble 'or ball level 43 which serves to indicate the side-slip" oi the craft on which the instrument is mounted.

The partsso far described are more or less common to all the different forms of the mechanism as will become apparent from the following description taken in conjunction with the drawings.

Movement of the scale ring 36 is brought about 46 to an air jet 53. Flow of air through the ducts 46, "is normally prevented by mushroom valves 54, having heads 56, 51 on the ends of their stems, which valves are spring-urged onto their seats by springs 56, disposed between the heads duct extends round to one of the inner gimbal,

56, 51 and the edge of the frame 4. A bifurcated element 59 is pivotally mounted at" and within a slot in this element engages a crank pin 6| on the arm 62 fast on the'shaft 63 which, extends forward through the front of the casing where it is provided with an operating head 64. A ring 65, provided with radial vanes 66, is mounted fast with the inner gimbal 2 or a ring of radial vanes may be mounted on or made integral with the 2 and 6, whilst the air from the jet 53 tends to blow it round-in anti-clockwise direction. By rotating the head 64 a quarter turn in clockwise direction, the member 59 is rocked in anti-clockwise direction about its-pivot 66 and so bears on and moves the head 56 thus opening the valve 54, whereupon air passes through duct 46, channel 46 and duct 56 to the jet 5|. The effect of the air issuing from the jet 5|, in attempting to blow the ring about a horizontal axis, is'to cause precession of the gyro-wheel I and rotation of the outer gimbal 3, about its vertical axis, and with it the scale ring 36. Rotation of the outer gimbal 3 is allowed to continue until the scale mark 31 of the desirednumeral 36 is opposite the nose of the pictured aeroplane 42 whereupon the head 64 is restored to normal-by a quarter tux-min anti-clockwise direction-to cut off from the Jet 51 by the closing of thevalve 54. To cause rotation of thescale in the opposite direction. the head 64 is turned a quarter tumin opposite (anti-clockwise) direction to cause the pin through duct 41, channel 49, and duct 52 to jet 1' 53. Anarrow 64' is provided on the head 64, which arrow stands vertically in the normal position of the head as in Figure 1 but otherwise .points in the direction in whichthe head 64 has and outer gimbals is* created mechanically, the

by rotation of the outer gimbal 3 about its ver- 3 chamber I through the duct 44 in the frame 4 to a chamber 45 therein. Ducts 46, 41 lead from the chamber 45 to annular channels 46, 49 respectiveiy. Aduct 56 in the extension I5 and gimbal 3 leads from the channel46 to an air Jet 6| and a similar duct 62 leads from the channel.

gyro-wheel and gimballing remaining as previously described. As previously described, .air is led into theback of the instrument (see Fig. 3) through filter gauzes 6 which cover the inlet duct 6 which passes through the solid frame 4 and communicates with the hollow vertical glanded pivot of the outer gimbal ring 3, from whence" the air is the gyro-wheel Ito rotate it.v The air passes out of the air-tight inner gimbal 2 through the other inner, gimbal pivot which is provided with the 16 parts 30 to 35 for the purpose previously described. The'solid frame also forms part of an outer air-tight instrument case and in this'embodiment comprises the back wall thereof.

The ring 65 having radial vanes 66 is also providedmounted on the pivotal axis of the inner .to the outer gimbal 3 (see Fig. 9), are arranged one on each side of the inner gimbal 2 with their free ends adjacent the varied ring 65. Fast with each lever I00, IN is a depending portion I04,

I05'slotted at I06, I01 to receive a pin I08,-I09 carried at the bifurcated end of a resilient lever or flat spring H0, HI, the,oth'er end of which is held by a lever H2, H3 pivoted at- H4, H5 also to the outer gimbal 3. K flanged ring H6 (Figs. 11, 12) is mounted for axial movement on the extension-or shroud I5. The bifurcated ends H1, H8 of a forked lever H9, conveniently'pivoted at I20 to an extension 4' of the frame 4, take about the ring H6 and are provided with steel rollers I2I which lie between the flanges of the ring H6 but are normally out of contact therewith. At its otherend the lever H9 is provided with two spring fingers I22, I23 (Fig. 12) disposed one on each side of a cam I24 on a shaft I journalled in the extensions 4 of the frame 4.

and adapted to be rotated by means of the conill] trol head 64. The cam I24 is so arranged that normally the forked lever I I9 is so positioned that the flanged ring H6 is ina normal position, but

when rotated by the head 65 a quarter turn in the one direction it raises the forked ends. H1,

lowers the same. The movement of the lever H9 causes the rollers to engage the flanges of the ring I I6 and raise or lower the same according to the direction of movement of the lever I I9. The cam I24 is substantially rectangular (Figures 14 and 15) in order that during its passage from one position to another it moves the spring arm acted upon to the required position -to move the flanged ring into the desired position--as is shown in chain line as regards the arm I22 in Figure l5and then allows a slight return movement of the spring arm-seen in full line-to remove the rollers I2I clear of the flange of the ring-H6. Thus, after reaching the adjusted position of,the flanged ring H6, the slight return movementof the spring arm (either "I22 or I23) and, consequentially, of the lever H9, the rollers I2I- are movedclear of the flanges of the ring H6 and do not hinder the free rotation thereof. The flanged ring H6 is maintained in normal and adjusted positions by means of pins I26, carried by a plate IiI fast with the ring H6, which pins extend through apertures in the part 3' of .the outer gimbal 3 (Fig. 12). Each pin I26v hasthree re- ..cess e s I28-.corresponding to the three possible positions of the ring I I6, i. e., raised, normal and loweredwith which engage the spring rods,l29

clamped onthe portion 3' of the outer gimbal 3 by screws I30. The plate I21 has oppositely directed extensions I27 and 121*.- On the extension I21 is mounted a pin I3I extending through having a portion H3 of larger diameter lying 1 of air controlled by valves.

under the lever II3 with its portion of smaller diameter extending therethrough such that when the ring H6 is raised the lever H3 is rocked upwardly about its pivot I I6 whereby the lever IOI is also raised. The free end of each of the levers I00 and I0 I is provided with a hinged .element I (Figs. 12, 13) normally maintained in horizontal position by a spring I36.when it rests'on an extension of the lever. During upward movement of a lever I00, IOI the element I35 engages one of the vanes 66 of the vaned ring 65 and due to the continued upward urge of the lever tends to rotate the varied ring whereby in efiect the gyro wheel precesses and the outer gimbal is rotated about its vertical axis. The. necessary resilience in the lever systems is' provided for by the flat springs H0, II I (Fig. 16) which flex tolallow movement of the levers I I2, H3 and to provide the continued urge of the levers I00, IOI during which the pins I01, I08 slide in the slots in the extensions I03, I04. The slot and pin also serve III from separating from the extensions I04, I05 so that when they are lowered the levers I00, IOI fall also. During downward. movement .ofthe raised lever, should the'element I35 engageor be obstructed by one or more of the vanes 66 it yields and passes the same without exerting any pressure thereon whichmight cause precession of the gyro-wheel. To prevent displacement of the levers I00, IOI-for example during inverted flyingeach is provided with a hair-pin spring I38 (Fig. 11) clamped thereon by a screw I39 and engaging a pin I40 on the outer gimbal 3, which also acts asia stop to'the'extensions I04, I05, which serves tov urge the levers I00, IOI into normal position. To set or re-set the scale 36 the pilot has only to rotate the head 64 a quarter turnin either clockwise or anti-clockwise'dire'ction-l-jto raise either the lever I00 or IOI by means of the parts H6 to I25 to cause precession of the gyro-wheel and rotation of the outer gimbal and scale ring nithe desired direction until the desired numeral is opposite the nose ofthe pictured aeroplane 42 whereupon he restores the head 64 to normal position. To ,hold the shaft I25 in to prevent the flat springs or resilient levers H0,

- normal and adjusted positions, a collar I4I (Fig.

I2)-having three peripheral recesses I42 (Fig.

13) corresponding to the three possible positions of the shaft I25is mounted. fast on the shaft f and the recesses 142 in the collar I are adapted to be engaged by a projection on a-spring I43.

In, Figure 17 is shown a further modification in which the couple betweenthe inner and outer gimbals is also brought'about by-means of jetsln' this embodiment the valves are actuated throughthe medium of a flanged ring similar to that in the embodiment last described with reference to Figures 8 to 16. As described in connection with,Fig 3, in the 1 modification illustrated in'Fig. 17, the motive air isled from the inlet duct through the channel 9, duct I'I, bore I2 and duct I6 of the plug I 0, past the ball I3 and so past grooves I in the periphery of the hard-steel bearing piece I4-into channel I5I and duct I 52 .to the chamber I53 from which extends the duct I8 leading to the hollow inner gimbal pivot as previously more fully described with reference to Figure'3. The jet 5| (Fig.1?) communicates via aductl54 with a chamber I55 communicating with the chamber I53, passageof air'from the chamber I53 to the chamber I55 normally being prevented by a valve I56. The other jet 52 communicates'via duct I51 with a chamber I 58 similarly communicating with the chamber I53 and having a valve I50. The stems I60, I6I of these valves I56, I59 extend out through the bottom of the chamber I53 and through apertures in an internal flange I62 in the flanged ring H6. The stem I60 is-provided with an end head I63 adapted to be engaged by the flange I62 when the flanged ring II6 is lowered to pulldown the valve I56 from its seating and allow air to pass from the chamber I53 to the chamber I55 and so to the jet 5|. The stem I60 also carries a'collar I64 and a coil spring I65 is disposed between the collar I64 and the flange I62, which spring urges the valve I56 onto its seat yet yields toallow upward movement of the flange I62. The stem I6I carries a collar I66 adapted to be engaged by the flange I62 when the flanged ring is raisedto lift the valve I50 ofl its l V prevents the air from issuing from that orifice seat to permit air to enter the chamber I58 and pass to the jet 53. A further collar I61 between which and the flange I62 is arranged a coil spring I68 to hold the valve onto its seat yet yield to permit downward movement of the flange I62.

The flanged ring H6 is raised and lowered by a lever II9, rollers m and the parts 122 to I of mechanismv in which the couplebetween the inner and outer gimbals is created by electromagnetic means. 6

Adjacent one of the .innergimbal pivots are disposed oppositely directed radial arms I80, I8 I which normally lie in a horizontal plane. From I84, I85 in any convenient manner under the.- control of a' switch actuated by the head 64,

adapted to close ,the circuit to either solenoid. The switch (not shown) will-thus have a normal dead position andalternate 1ive" positions'ior completing either of the electric circuitsior example the control member '(head- 64) of the switch may be moved from normal position either to the right or to the left according to the direction of movement it ,is desired to impart to the scale.

When current is passed through one of the solenoids I84, I85 it exerts a pull on its armature which, acting through the arm, tends to rotate the inner gimbal about its pivotal axis. -This effort causes precession of the gyro-wheel which causes the outer gimbel to rotate about its pivotal axis and with it rotation of thescale ring'carried thereby. When the scale has been re-set to zero or set to the desired position, the current is switched oil. It will be appreciated that the pilot has merely to move the switch control-memher in the appropriate direction andthen restore it to normal at the correct moment, Just as in the other embodiments, the setting or re-setting of the scale thus requiring no maintained manual effort on his part. v

Whilst it is preferred to employ two solenoids which are separately energized, a single polarised solenoid may equally well be employed in which case the weight of its armature may be counterbalanced. In this embodiment the Ey O-wheel may be driven-by air, for example as previously described or byelectricity in the known manner. In the various embodiments so far described, the inner gimbal is erected with respect to the outergimbal-by the parts 28 to35 but in any of the different forms the inner gimbal could be erected to the true horizontal. Controlling means for this purpose are shown in Figure 20, comprising a controlivalve consisting of a ball I10 free-to move in a chamber I1I into which the air enters from the casing 2 through ports I12 in 10 its side in the region of the. middle thereof. The

channel 'I1 I is reduced in diameter at each end,

and form the emergent air orifices I18, I14, through which orifices I13, I14 the 'air issues into the outer case in the form of Jets. Should the i5 inner gimiial tilt,-the ball I10 rolls by gravity against the constriction at the lower end and whilst allowing the air to emerge from the other,

so producing-an, unbalance'oi the air jets which 20 react upon'the air in the instrument case and so sets up an erecting torque for restoring the inner gimbal to the true horizontal.

What I claim is:

gimbal being pivoted about a horizontalaxis at right angles to thespin' axis-of said rotor, an

outer gimbal pivoted abouta vertical axis and 30 carrying said inner gimbal, a scale ring carried by saidouter gimbal, mechanical means for cre-' ,ating a couple between said inner gimbal and said outer gimbal to 'causesaid 'outer gimbal to rotate about its vertical axis, said mechanical means comprising springs mounted on opposite sides of the outer gimbal, levers mounted on the same gimbal as the springs and on opposite'sides oi the rotor, each lever being connected to a spring to be rocked thereby, a-displaceable end 40 piece on each lever, said end pieces being displaceably mounted in one direction so as to pass obstacles when moved inthat, direction, abut-1 ments attached to the-inner gimbal and comprising a vaned ring having its vanes disposed 45 radially oi the axis of said ring for engagement by said end pieces, the latter being displaced andpassing said vanes upon movement of said levers in one direction, while pressure is exerted on said vanes by said end pieces upon movement of said so levers in reverse direction, resilient means for holding said levers in a normally,rest position with the end pieces exerting no operating pressure on said vanes, and a flanged ring ope'ratively connected with said springs, the displacement of as saidgring imparting movement to said springs and the levers connected thereto.

2. A gyroscopic navigating instrument, as

' claimed in claim 1, in which the said levers are arranged for operative engagement with said (so flanged ring so that-aqdisplacement of the latterin one direction out. of rest position elevates one, lever and movement in theopposite direction out or rest position elevates the other lever.

movement in the opposite-direction-out oi rest 70 position elevates the other lever, and means tor displacing the said flanged ring comprising a forked'lever, and a cam to control the forked lever.

4,-A gyroscopic navigating instrument, "as is 1. Ina gyroscopic navigating instrument, an 25 innergimbal, a rotor spinning about a horizontal axis andcarried by said inner gimbal, said inner.

3. A gyroscopic navigating instrument, as 6.3

claimed inclaim 1, in which the said levers are arranged for engagement withsaidflanged ring so that displacement thereof in one direction out of rest position elevates onelever and movement in the opposite direction-out of rest positionelevates the other lever, and means for displacing.-

the. said flanged -ring comprising a movable forked lever' and a cam to control the movement of said forked lever, said cam having a profile adapted to move the forked lever after the same has'moved the fian'ged ring out of contact with the latter. v a A 5. In a directional gyroscope of the type in- A cluding an instrument casing, a vertical ring mounted insaid casing for rotation in azimuth, a gyro frame mounted in said vertical ring for oscillation about a first horizontal axis, a gyro rotor journaled in said frame for spinning about a second normally horizontal axis perpendicular vto said spin axis,-'and acompass card carried by -and rotatable with said vertical ring, the com-' bination' with said gyroscope of means forresetting said vertical ring and compass-card by causing precession of said vertical ring in either 5 direction in azimuth without'locking said gyroscope, said resetting means comprising mechanical-means in said casing for producing a torque on said gyroscope in either direction about said first horizontal axis, mechanical means insaid 80 casing engaging and directly controlling said torque producing means, and means including a manually actuated shaft extendingfromthe ex terio'r of said casing into the interior'thereof' and.

engaging-said controlling 'means to actuate the latter and thereby cause said torque producing means to producea torque on-said gyroscope in one direction or the other about said first horizontal'axis'.

6. In-a directional gyroscope ofthetype in-- cluding a v vertical'ring mountedfor rotation in azimuth, a gyro frame mounted in said vertical ring for oscillation about a first horizontal axis,

a gyro rotor 'joumaled in said frame'for spin"- ning about a second normally horizontal axis at right angles to said spin axis, the combination withsaidgyroscope of means for .resetting'the same by causing precessionof said vertical-ring in either direction it? azimuth without locking said gyroscope, said resetting means comprising mechanical means for producing a torque on said gyroscope in either direction about said first horizontal axis, mechanical means engaging'and directly controlling saidtorq-ue producing means,

and manually actuated means engaging said controllingmeans to actuate the latter and thereby cause said torque producing means. to produce a torque on said gyroscope in one direction or the. i

other about said first horizontal axis.

7. In a directional -gyroscope of the type including an instrument casing, a vertical rin'g mounted in said casing for rotation in azimuth,

i a gyro frame mounted in said vertical ring. foroscillation about a first horizontal axis, and a gyroscopicizrotor, Journaled in said frame for spinning about a secondnormally horizontal axis 4 axis, means for applying'a force to said vanes,

.on either side of said first horizontal axis, vmeans for controlling said force applying means, and

means including a'manuallyactuated shaft extending'from the exterior of the casing into the interior thereof and directly engaging said con-. trolling means to actuate said force applying.

means.

'8. In a directionalgyroscope of "the type including an' instrument casing, a vertical ring mounted in said casing for rotation in azimuth,

a gyro frame mounted in said vertical ring for oscillation about a first horizontals-axis, and a gyroscopic rotor journaled' in said Iframe for j spinning about a second normally horizontal axis perpendicular to said first horizontal axis, the

combination with said gyroscope of means for resetting the same by causing precession of said vertical ring in either direction in azimuth without looking said gyroscope, said resetting means comprising a vaned ring carried by said gyro frame concentrically with the first horizontal axis', means for applying a force ,to the vanes of said ring on either side of said first horizontal axis, means directly controlling said force producing means, a manually actuated shaft extending from the exterior of the casing into the ins terior thereof, and a cam carried by said shaft and engaging said controlling means for actuating the same to produce a force on the vanes .of said vaned ring on one side orthe other of said first horizontal axis.

' 9. In a directional gyroscope of thetype including an instrument casing, a've'rtical ring mounted in said casing for rotation in, azimuth, a gyro frame mounted in said vertical ring for oscillation about a first horizontal-axis, and a gyroscopic rotor iournaled in'said frame for spin ningabout a second normally horizontal axis perpendicular to said first horizontal axis, the

combination with said gyroscope of means for revertical ring in either direction iniazimuth with-.

setting the same by causing precession-of said I out looking saidgyroscope, said resetting means comprising a i'vaned ringcarried by said gyro frame concentrically with said first horizontal axis, means for'producing an .air 'Jet impinging against the vanes ofsaid vaned ring on. one side of said-first horizontal axis, means for producing an air jet impinging against the vanes of said Y vaned ring on the opposite side of said horizontal axis, valve means for controlling both of said air jet means, a manually actuated shaft, extending from. the exterior of the, casing into the interior thereof, and means including ajcam actuated by said shaft for actuating said valve means.

- 'r oUGLAS. GEORGE KING Moss" 

